Mitsubishi Electric MELSEC iQ-R Series User Manual page 162

Redundant function
The following table lists the special register areas relating to the redundant function.
: Can be set, : Cannot be set
No. Name
SD1643 System switching
cause
SD1644 Cause of system
switching failure
SD1648 Cause of the other
system monitoring
error
APPX
160
Appendix 4 List of Special Register (SD) Areas
Description Details
System switching System switching cause occurred in own
cause occurred in system is stored. The system switching
own system cause is stored in this register even if the
systems cannot be switched by a cause of
system switching failure.
This register is cleared to 0 when the system
is powered on and off or reset.
0: Initial value (the control system never
been switched)
1: Reset or hardware failure of the remote
head module
2: Moderate error or major error
3: System switching due to data link error
16: Follow the system switching of the
redundant line master station.
17: System switching request from the
engineering tool
When the systems are switched by resetting
the control system, "1" is not stored in 'Cause
of system switching' (SD1643) of the new
standby system.
Cause number of Error cause in the control system is stored in
system switching this register when a system switching is
failure failed.
0: System switching completed normally
(default)
1: The standby system is not available for
communications. (The standby system is in
reset processing or not connected.)
2: Communication timeout
3: Moderate error or major error in the
standby system
4: Both systems operate differently.
5: Memory copy from the control system to
the standby system being executed
7: Data link error is detected in the standby
system.
8: System switching being performed
9: Online module change being performed
• When own system is powered on, this
register is cleared to 0.
• When the system switching is completed,
0 is stored in this register.
Cause of the other The following corresponding bit turns on
system monitoring when communication error occurs in the
error other system. That bit turns off when the
error is cleared after that.
Each bit turns on when the value is "0" and
off when the value is "1".
b0: Fixed to 0
b1: Reset or hardware failure in the other
system
b2: Moderate error or major error in the other
system
b3 to b14: Fixed to 0
b15: The other system is not available for
communications.
• If any of b1, b2, and b15 is on, the other
bits are off.
• When the other system is reset or in a
hardware failure, b15 may turn on
depending on the timing.
Set by (setting Effective system
timing)
Control
system

S (System switching)

S (System switching)

S (Every END/system
switching)
Standby
system


